The present invention relates to a magnetic recording head provided with a single pole perpendicular recording head and its fabrication method.
Hard disk drives that are magnetic recording/reproducing devices employed as external recording devices of such information processing apparatuses as computers, etc. are getting more and more increased in capacity and reduced in size, so that those hard disk drives themselves have also been improved mainly in recording density to cope with such improvement. On the other hand, the conventional longitudinal magnetic recording method has been found not to be able to cope with such high recording density requirements. This is because the conventional longitudinal magnetic recording method, when it is to be applied to realize such high recording density, comes to be required to reduce the recording layer in thickness more to cope with the large anti-magnetic field to be generated in the magnetization transition region on the subject medium. If the recording layer is reduced in thickness, the recorded data comes to be erased by thermal confusion. This has been a problem. On the other hand, the perpendicular magnetic recording method, in which the recording layer is magnetized in the direction of the film thickness of the subject medium, makes it easier to achieve the high recording density, since the anti-magnetic field is small in the magnetization transition region, so that the medium is not required to be reduced as much in thickness.
If a so-called perpendicular magnetic recording head (single pole type head) is used to record signals on a perpendicular magnetic recording medium, the electric signals are converted to magnetic signals by a coil and a magnetic flux is excited in both of the main pole and the return pole respectively. A part of the magnetic flux passes through both of the return pole and the main pole, then passes through the perpendicular recording layer of the recording medium. After that, the magnetic flux passes through the soft underlayer formed as a lower layer of the perpendicular recording layer to go back to the return pole just like drawing a closed loop. At that time, the return pole functions to transfer the magnetic flux generated in both of the perpendicular recording layer and the soft underlayer of the recording medium from the main pole to the main pole efficiently. Such a flow of the magnetic flux records magnetized signals on the perpendicular recording medium. The official gazette of JP-A No. 279607/2002 discloses an example of such magnetic recording heads.
Meanwhile, the surface recording density of the perpendicular magnetic recording head has also been improved. Along with the improvement of the surface recording density, it is now desired to reduce the recording track in width while information must be recorded/reproduced widely from inner periphery to outer periphery of the subject magnetic recording medium in each magnetic disk drive. However, information is recorded/reproduced by the magnetic recording head at a skew angle of about −15 to 15° to the tangential line of the medium in the rotational direction at both inner and outer peripheries of the medium. At that time, if the main pole is shaped like a rectangle on the air bearing surface of the main pole, the width of the recording track cannot be reduced. To solve this problem, therefore, a method is proposed to reduce the leading side magnetic pole in width more than the trailing side magnetic pole, thereby narrowing the track in width.
The official gazette of JP-A No. 92821/2002 discloses a method for forming a magnetic recording head having a track that becomes narrower at the main pole leading side than at the main pole trailing side of the main pole on the air bearing surface. According to the method, such a structure is realized by forming a resist frame on a non-magnetic insulation film, then forming a trench in a reactive ion etching (RIE) process. After that, the trench is plated with a magnetic film, then the main pole shaped like an inverted trapezoid is formed in a chemical mechanical polishing (CMP) process.
The official gazette of JP-A No. 197609/2002 discloses another method for forming a main pole shaped like an inverted trapezoid as follows: at first a resist frame is formed on a plated underlayer, then both of the magnetic film and the non-magnetic film are plated. The official gazettes of JP-A No. 208112/2002 and JP-A No. 242608/2003 also disclose a method for forming a main pole shaped like an inverted trapezoid by depositing a non-magnetic film on a magnetic film, then forming a resist frame and plating it thereon, and finally dry-etching the film. The official gazette of JP-A No. 208112/2002 discloses still another method for forming a main pole by subjecting the substrate to an ion milling process while the substrate is vibrating within a range of +90 to −90° with reference to a direction in which an ion beam is oriented from the medium to the air bearing surface. The official gazette of JP-A No. 242608/2003 discloses a method for forming a magnetic recording head that is rectangular in shape at its magnetic flux introduction part. According to those fabrication methods, an ion beam is applied to the substrate at an angle of 45° and over from the normal line side of the substrate respectively.